As an example of a process requiring an aqueous liquid-gas contact apparatus, the Wellman-Lord process of sulfur dioxide removal from stack gases employs an aqueous alkali sulfite solution (usually sodium sulfite) which chemically combines with the sulfur dioxide gas in an absorption tower by forming sodium bisulfite. The process includes a separate regeneration facility to convert the bisulfite back to sulfite and recover sulfur dioxide gas which is compressed and bottled or converted sulfuric acid or to elemental sulfur. In the case of flue gases from coal fired plants, a separate unit for removal of fly ash and chlorides is included.
Because of large capital costs and high energy requirements to overcome the pressure drop in the absorber, in the regenerable Wellman-Lord process, non-regenerable flue gas desulfurization processes have been the more popular choice in the past, in spite of the major problem of disposal of solid waste produced by such processes.
The present invention is an improvement in absorption apparatus and its operation and in particular the process of the invention relates to the absorber of the Wellman-Lord process whereby capital costs and parasitic power requirements are reduced so as to make the regenerable process more economic and thus avoid the solid waste problem of the non-regenerable processes.